Guide Replit
How do I secure a Replit app that uses Supabase?
Short answer
It depends on where your app talks to Supabase. If the browser calls Supabase directly with supabase-js, Row Level Security (RLS) is what protects your data, so every table needs RLS on and owner-scoped policies. If only your Replit server talks to the database, keep the secret key or connection string in Replit Secrets and make sure every API route checks who the user is. Either way: keep service_role and sb_secret_ keys out of frontend code, run Replit's security scans before you publish, and test with a second account.
1. Find out where Supabase is called
Search your project for createClient(. If it runs in files the browser loads (React components, client/, anything bundled by Vite), the browser talks to Supabase and RLS matters. If it only runs in server code (an Express or FastAPI server), your API routes are the gatekeeper. Many Replit apps do both.
2. Keep keys in Replit Secrets
Replit's Secrets tool encrypts values and exposes them to your app as environment variables. Replit warns that hard-coded secrets leak when you share a public project, push to a public repo or screen-share. Put the Supabase secret key and any database connection string there, and read them only in server code. The publishable or anon key is designed to be public, so it's fine in the browser.
3. If the browser calls Supabase, fix RLS
Open the Supabase Security Advisor and fix every "RLS Disabled in Public" error. Then make sure private tables use owner checks like (select auth.uid()) = user_id. Examples: Supabase RLS policy examples.
4. If your server talks to the database, check every route
A server using the secret key or a direct connection bypasses RLS, so the server must check that the signed-in user owns what they ask for. Look for routes like /api/orders/:id that return a row by id without comparing it to the current user. Supabase's Oct 30, 2026 grants change does not affect direct Postgres connections, only the Data API.
5. Run Replit's security scans
Replit's Security Center has three scan levels: Level 1 checks packages for known vulnerabilities, Level 2 adds an Agent review of your source code, and Level 3 tests the live preview from outside. Agent scans are for paid plans. Replit's own docs say: "No scan guarantees that your app is secure." Under Replit's shared responsibility model, reviewing the security of Agent-written code is your job.
Where we can help
Free instant check: paste your URL at patchandship.com/check.html to scan your homepage's JavaScript for secret keys and security headers (no signup, nothing stored). Paid, fixed price per app: Database Check, $49; Security Fix, $149 (every critical issue on our checklist fixed within 48 hours of working access); Fix & Deploy, $249. Otherwise a full refund if you ask within 14 days of purchase (Refund Policy). AI agents run the checks and a human engineer approves every change. Not a penetration test or a security guarantee.
FAQ
Is the Supabase anon key safe in a Replit frontend?
Yes, if RLS is right. It's designed to be public. The secret and service_role keys are not, because they bypass RLS.
Are Replit Secrets visible to people who remix my app?
Replit's docs say Secrets let you share code without exposing credentials, but collaborators you give edit access can be allowed to view secrets. Rotate keys after removing a collaborator.
Do I need RLS if only my server talks to Supabase?
RLS is still a good backstop, but the real protection is your server's authorization checks, since the secret key bypasses RLS.
Does a clean Replit scan mean my app is secure?
No. Replit says no scan guarantees security. Test with two accounts and a signed-out request too.